Sprocket-driven chains are used in a variety of different applications. Some applications require the chains to operate in highly abrasive environments. One example is the use of chains in trenching operations, where various cutting or abrading attachments are included on the chain. In operation the chain is revolved about an extended arm or boom, and lowered into contact with the ground. When removing the soil, rock or other ground material, abrasive material comes into direct contact with the links of the chain. Similarly, chains used in conveyor or elevator operations may also be exposed to abrasive or corrosive materials. In both examples, if the abrasive material gets into the joint formed between the pins and sidebars of the links an early failure may occur, sometimes after mere hours of operation.
Several approaches have been suggested in the past for dealing with this general problem. One such can be seen in U.S. Pat. No. 4,094,515. This patent discloses, in one embodiment, the use of an annular rubber seal having an x-shaped cross-section, disposed between inner and outer sidebars of roller chain. The seal serves to both prevent the leakage of lubricant, used between the pin and bushing, and the ingress of dust. However, where a rubber seal of this type is exposed to more abrasive or corrosive materials than dust, it may itself become a point of early failure.
Another approach is disclosed in U.S. Pat. No. 5,269,729. This patent narrowly teaches the use of a two-element seal, with a first outer element having an annular groove and an inner resilient-ring element of uniform (circular or x-shaped) cross-section fitting within the annular groove. The structure of the outer metallic element is required to keep the second resilient element in relative position. Thus, such a two part structure is more costly and less convenient to make and maintain than older single-resilient seal approaches, such as taught in U.S. Pat. No. 4,094,515 (which, while more convenient, were much less resistant to early abrasion-induced failure).
Just such a solution to the problems noted above and more, are made possible by my invention disclosed here.